title: Likelihood of aneurysmal subarachnoid haemorrhage in patients with normal unenhanced CT, CSF xanthochromia on spectrophotometry and negative CT angiography.
abstract: BACKGROUND
  Patients with suspected subarachnoid haemorrhage, a normal noncontrast computed tomography (CT) and cerebrospinal fluid (CSF) evidence of haemoglobin breakdown products often undergo CT angiography (CTA). If this is normal, then invasive catheter angiography may be offered. In current clinical practice, haemoglobin breakdown products are detected by spectrophotometry rather than visible xanthochromia, and CTA is performed on multidetector scanners. The aim of this study was to determine if such patients should still have a catheter angiography, given the associated risks.
  
  
  METHODS
  Patients positive for CSF spectrophotometry (n=26) were retrospectively identified from the clinical biochemistry information system and imaging data from the electronic radiology records were reviewed. Discharge letters were consulted to relate the biochemistry and radiology results to the final diagnosis.
  
  
  RESULTS
  15 patients with CT angiography were found. Nine patients had normal CT angiography. No causative aneurysms had been missed. One patient had small, coincidental aneurysms missed on initial reading of the CTA.
  
  
  CONCLUSIONS
  The likelihood of a clinically significant aneurysm in a patient who is CT negative, lumbar puncture positive and CTA negative is low. Double reporting of negative CT angiograms may be advisable.
authors.affiliation: AK Rana, Aberdeen Biomedical Imaging Centre, University of Aberdeen Lilian Sutton Building, Foresterhill, Aberdeen AB25 2ZD, UK. arnab@imagingsense.com.
authors.forename: A K
authors.initials: AK
authors.lastname: Rana
authors.forename: H E
authors.initials: HE
authors.lastname: Turner
authors.forename: K A
authors.initials: KA
authors.lastname: Deans
mesh_terms: D000368:Aged; D002533:Cerebral Angiography / Q000379:methods; D006454:Hemoglobins / Q000134:cerebrospinal fluid*; D006801:Humans; D012189:Retrospective Studies; D013053:Spectrophotometry; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D006454:Hemoglobins
keywords: Angiogram-negative subarachnoid haemorrhage; spectrophotometry; subarachnoid haemorrhage; xanthochromia